Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Would you make your own kiln?

  • Please log in to reply
83 replies to this topic

#1 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 December 2018 - 10:55 AM

If I can built something for close to the cost of store bought after my time is factored in, then I'd rather learn how to make it and proudly say I made it.

I'm guessing how hard it is to make one depends on the tools already on hand and on the design. Are the raw materials expensive?

I read some only last 400 cycles. I wonder how much it cost to just replace the part that breaks.

Also, I wonder how much heating is from radiation and how much from conduction/convection. For convection, where does the expanding gas go? I read the energy used is not that expensive though. For radiation, how evenly is the heating distributed?

Cycles take time, so single blanks are expensive time wise. I wonder how placing multiple moulds in a kiln affects the heat transfer and temperature of each one. Maybe multiple filaments solves that. The hottest air would gloat to the top. Any pressure release should be at the bottom.

Edited by stargazer193857, 27 December 2018 - 11:04 AM.


#2 nstiesi

nstiesi

    Mariner 2

  • *****
  • Posts: 263
  • Joined: 21 Mar 2016

Posted 27 December 2018 - 11:11 AM

I'm not sure about a "kiln", or how close in use it would be to a "forge"....are those terms interchangeable?

Seems to me it's about how much mass you need to heat, and how hot it needs to get.

I built a small "one brick forge" a few months back out of 2600° IFB (insulated fire brick). I use it to heat high carbon steel for annealing or hardening when making knives. It is fired with a small MAP PRO torch.

When researching this project, I saw plenty of larger designs meant for even melting and casting the metal itself.

As always, BE SAFE, whatever you do. The little knife forge was dangerous enough.....I always keep a fire extinguisher closer by.

I have a video somewhere, I can post it if interested.

Sent from my Moto G (4) using Tapatalk

#3 555aaa

555aaa

    Vendor (Xerxes Scientific)

  • *****
  • Vendors
  • Posts: 1,578
  • Joined: 09 Aug 2016
  • Loc: Lynnwood, WA, USA

Posted 27 December 2018 - 11:16 AM

What are you intending to do with this kiln? How big?

#4 starcanoe

starcanoe

    Vanguard

  • *****
  • Posts: 2,487
  • Joined: 07 Nov 2013
  • Loc: Gulf Coast, Panhandle of Florida

Posted 27 December 2018 - 11:33 AM

Like pretty much all interesting stuff....a kiln is more expensive, dangerous, and complicated than one might suspect at first glance..lots of research and caution are advised (what people did before the internet is almost mind boggling these days).

 

I always wondered if in the late 80 some spy satellite detected a possible missile launch in lower Alabama on a couple of nights...


  • Jon Isaacs, Dave O and stargazer193857 like this

#5 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 December 2018 - 12:01 PM

Like pretty much all interesting stuff....a kiln is more expensive, dangerous, and complicated than one might suspect at first glance..lots of research and caution are advised (what people did before the internet is almost mind boggling these days).

I always wondered if in the late 80 some spy satellite detected a possible missile launch in lower Alabama on a couple of nights...


To be able to launch your own rocket back in the days before you could get caught ...

#6 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 December 2018 - 12:07 PM

What are you intending to do with this kiln? How big?


I want to slump 1/2" x 12" boro glass blanks to spherical 1/6" inch deep curve, then anneal them on the cool down, and have 4 moulds in there on steal shelves so I get more for my multi-hour process.

I'm guessing there are designs posted somewhere. I don't want just any kiln. I want to design one optimized for my purpose, and maybe not pay the $500-$1000 entry fee.



Yeah, a forge is for metal, and goes hotter. I wonder if I should make a metal spider sling instead of a mold.

#7 TOMDEY

TOMDEY

    Fly Me to the Moon

  • *****
  • Posts: 5,673
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 27 December 2018 - 12:35 PM

Sounds like FUN!

 

Just like grinding, polishing, figuring... it's half science and half art. My son built and ran kilns for ten years, all kinds of glass... including BIG stuff. His Glass Science degree helped, of course. Like any technology, there's a LOT more to getting it controlled, consistent and right... than might seem. Also the eventual cost can be a tiger by the tail.

 

Can say the same thing for figure skating, running marathons, playing an instrument. There's good, Good and GOOD!

 

ANECDOTE: I designed, successfully prototyped, and patented this optical gizmo that would need slumped mirrors for the "production models".  My prototype was about a foot across. The Real ones would be Eight Feet across!  The experts broke several before finally getting the slumping and annealing ovens, heaters and schedules on target. We made the real Gizmos and they are... preforming nicely!

 

It's Scary when you're developing something that "must work... by THIS date... within This cost..."  Total development time was around a year. And we got First Light... a Whole Day Early!  Tom

 

But, it's a hobby for us --- Go For It!  And buy a Lot of glass...    Tom


  • Dave O likes this

#8 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 December 2018 - 01:55 PM

Yeah, I think patents do more harm than good. Often they are made by people who can't bring the product to market, have not worked out the details, want a million dollars, and have broadly claimed it so no functionally similar invention can be brought to market.

I once invented a simple silent rachet but could not sell it because someone else designed one of such complexity that I doubt they built it or that anyone could know if theirs would even work. Yet their specific claim lets them make a broad claim to include all else including my simple design.

I believe to get a 20 year patent, one should have a working marketable model. Otherwise they should just get a year to make it work. But that is another trade-off issue.

I hope slumped mirrors have not been patented.




Yes, I'll have fun. If I can't go hiking with my bad knee, I might as well explore materials science in my shop while on my wheely chair.
  • Dave O likes this

#9 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 December 2018 - 01:59 PM

If the holder has a year, they can show it to 5 companies and ask which one of them wants a 20 year patent for building what the holder can't, or if they want to compete with each other in a year, or see if the inventer can build it himself. Even 2 years. If the company does not want to wait 2 years, they can prove the design does not work.

#10 totvos

totvos

    Viking 1

  • *****
  • Posts: 617
  • Joined: 09 Sep 2015
  • Loc: Mississauga, ON, Canada

Posted 27 December 2018 - 02:01 PM

You would only make your own kiln if the size you wanted was prohibitive to buy. It is easy and cheap to find small(er) ceramic kilns used on Craigslist, and then add the necessary digital controller onto them. All in, maybe $300. Once you get to larger glass, the dimensions of a ceramic kiln become prohibitive, and you might be better off rolling your own.



#11 mark cowan

mark cowan

    Vendor (Veritas Optics)

  • *****
  • Vendors
  • Posts: 9,525
  • Joined: 03 Jun 2005
  • Loc: salem, OR

Posted 27 December 2018 - 02:01 PM

If you make it bigger to hold more blanks for annealing it takes more energy to heat it - yeah, there's some advantage to more-than-one capacity but it's mostly time since you would have to run it multiple times otherwise.  But for slumping you run one at a time since the control has to be exact for it to work and typically the base of the kiln is made to receive the slumping mold - which may not be possible on shelves.


  • TOMDEY likes this

#12 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 December 2018 - 02:08 PM

One at a time certainly makes local temperature control a non issue. But I'm reading about glass being in a kiln for at least 4-5 hours. Having 4 moulds in there stacked would really save time if it could be done.

OTOH, even if the kiln does 3 per day, 4-5 hours each, that likely is all I can hope to polish and sell.


Used on Craigslist sounds good.

I would not make it bigger but rather just put an inch gap between blanks. I bet more energy is in the glass than in the air. The real price point though is the cost of the kiln vs the time it is full and in use. I read the energy is not that expensive, though I'd have to calculate that myself.

Edited by stargazer193857, 27 December 2018 - 02:23 PM.


#13 dmcnally

dmcnally

    Vendor - Dave's Astro Shop

  • *****
  • Vendors
  • Posts: 916
  • Joined: 16 Mar 2012
  • Loc: Lompoc, CA

Posted 27 December 2018 - 02:26 PM

You would only make your own kiln if the size you wanted was prohibitive to buy. It is easy and cheap to find small(er) ceramic kilns used on Craigslist, and then add the necessary digital controller onto them. All in, maybe $300. Once you get to larger glass, the dimensions of a ceramic kiln become prohibitive, and you might be better off rolling your own.

I agree that it's better to buy one, but I don't agree that you can get one for $300 off CL.  I've looked in SoCal and the going rate is $500 to $1,000 for a decent kiln and that's without a programmable controller (i.e. add more $$$$).

 

Dave



#14 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 December 2018 - 02:28 PM

Another idea is mutible compartments inside the small kiln, like a stack of pancakes, trapping warm air from rising to the next level, and each level having its own tungsten fillament zig zagging above the blank. I read the mould needs air holes drilled in it.

I think I can make this work.

#15 mark cowan

mark cowan

    Vendor (Veritas Optics)

  • *****
  • Vendors
  • Posts: 9,525
  • Joined: 03 Jun 2005
  • Loc: salem, OR

Posted 27 December 2018 - 02:31 PM

One at a time certainly makes local temperature control a non issue. But I'm reading about glass being in a kiln for at least 4-5 hours. Having 4 moulds in there stacked would really save time if it could be done.

OTOH, even if the kiln does 3 per day, 4-5 hours each, that likely is all I can hope to polish and sell.


Used on Craigslist sounds good.

I would not make it bigger but rather just put an inch gap between blanks. I bet more energy is in the glass than in the air. The real price point though is the cost of the kiln vs the time it is full and in use. I read the energy is not that expensive, though I'd have to calculate that myself.

More like a week not 4 or 5 hours.  :lol:


  • Jon Isaacs, PrestonE, Oregon-raybender and 1 other like this

#16 brave_ulysses

brave_ulysses

    Apollo

  • -----
  • Posts: 1,275
  • Joined: 19 Apr 2009
  • Loc: far outside the wire

Posted 27 December 2018 - 02:56 PM

paid $100 in north texas for a paragon kiln with accessories a few years ago

 

deals still appear

 

add ssr control and 2-3 thermocouples and you have a great start

 

 

 

 

Attached Thumbnails

  • kiln.png

  • Earthbound1 likes this

#17 TOMDEY

TOMDEY

    Fly Me to the Moon

  • *****
  • Posts: 5,673
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 27 December 2018 - 03:57 PM

Yeah, I think patents do more harm than good. Often they are made by people who can't bring the product to market, have not worked out the details, want a million dollars, and have broadly claimed it so no functionally similar invention can be brought to market.
I once invented a simple silent rachet but could not sell it because someone else designed one of such complexity that I doubt they built it or that anyone could know if theirs would even work. Yet their specific claim lets them make a broad claim to include all else including my simple design.
I believe to get a 20 year patent, one should have a working marketable model. Otherwise they should just get a year to make it work. But that is another trade-off issue.
I hope slumped mirrors have not been patented.
Yes, I'll have fun. If I can't go hiking with my bad knee, I might as well explore materials science in my shop while on my wheely chair.

I have 40+ so far, some already expired. The rules (United States) have been tweaked to encourage/require transition to production, else the patent gets free license to others... something to that effect (Good!) Most of the places where I worked, or contract to... would not even consider patenting unless we were rocketing into production ASAP. Just sitting on patents is pretty much a thing of the past.

 

Prototyping was By Far the most fun part of the entire process! >>>

 

>team gets assigned another "Impossible Problem"

>anyone/everyone dreams up solutions (the crazier the better!)

>concepts enter committee, nearly all get shot down, couple/few get the go-ahead

>champions sweat bullets, arses and reputations on the line

>patent applications

>prototyping

>more hurdles, convincing

>customer awards production contract

>produce, test, deliver

>deployment...

>first light

>success or failure

 

FUN!    Tom

 

Ummm... I don't think you need worry that slumping is any longer patent-protected !

 

~~~

 

An Improved Mouse Trap:

...

6. The apparatus claimed in claim 1, wherein the slumping boule descends upon the mouse, igniting it beyond survivability.

...


  • Jon Isaacs, PrestonE, stargazer193857 and 1 other like this

#18 totvos

totvos

    Viking 1

  • *****
  • Posts: 617
  • Joined: 09 Sep 2015
  • Loc: Mississauga, ON, Canada

Posted 27 December 2018 - 07:58 PM

More like a week not 4 or 5 hours.  lol.gif

Yeah, what he said, My kiln runs are a somewhat aggressively short 42 hours.



#19 totvos

totvos

    Viking 1

  • *****
  • Posts: 617
  • Joined: 09 Sep 2015
  • Loc: Mississauga, ON, Canada

Posted 27 December 2018 - 08:00 PM

I agree that it's better to buy one, but I don't agree that you can get one for $300 off CL.  I've looked in SoCal and the going rate is $500 to $1,000 for a decent kiln and that's without a programmable controller (i.e. add more $$$$).

 

Dave

You just need to keep looking. As posted above, I got a similar Paragon kiln, PLUS another one without a lid, for C$120. My PID was from Ebay for C$150, including thermocouple.



#20 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 December 2018 - 11:48 PM

I'll definitely have to educate myself on some glass thermo physics and specific numbers, though my plan is to use 1/2" thick glass, not 1.5" or 2".

Hmmm... maybe I should be sure the air exposed side and mould side are exposed to equal temperature. Again, I need to study the thermal physics. And need to know specific values for the needs of a telescope mirror.

Absent such info, the other option is to experiment, starting at recommended values and seeing which blanks need to go back in when figuring gets difficult.

#21 mark cowan

mark cowan

    Vendor (Veritas Optics)

  • *****
  • Vendors
  • Posts: 9,525
  • Joined: 03 Jun 2005
  • Loc: salem, OR

Posted 28 December 2018 - 10:30 AM

OP - have you made a lot of mirrors? 

 

I only ask because it seems to me you're vastly underestimating the inherent difficulties of a lot of the process involved...


  • TOMDEY and Garyth64 like this

#22 stargazer193857

stargazer193857

    Cosmos

  • *****
  • topic starter
  • Posts: 8,041
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 28 December 2018 - 04:15 PM

OP - have you made a lot of mirrors?

I only ask because it seems to me you're vastly underestimating the inherent difficulties of a lot of the process involved...

Your right. It is time for me to build one. I'll start with 10" f5 0.75" plate. This will be interesting and educational. I'll then have a much better idea what I'm up against with thin mirrors.

The next time I post on this forum is when I have pictures of the blanks. (I'm getting the kit and plan to grind both separately.)

Edited by stargazer193857, 28 December 2018 - 04:27 PM.

  • mark cowan likes this

#23 Garyth64

Garyth64

    Skylab

  • *****
  • Posts: 4,397
  • Joined: 07 May 2015
  • Loc: SE Michigan

Posted 28 December 2018 - 05:15 PM

I'll definitely have to educate myself on some glass thermo physics and specific numbers, though my plan is to use 1/2" thick glass, not 1.5" or 2".

Hmmm... maybe I should be sure the air exposed side and mould side are exposed to equal temperature. Again, I need to study the thermal physics. And need to know specific values for the needs of a telescope mirror.

Absent such info, the other option is to experiment, starting at recommended values and seeing which blanks need to go back in when figuring gets difficult.

popcorn.gif


  • okiestarman56 likes this

#24 starcanoe

starcanoe

    Vanguard

  • *****
  • Posts: 2,487
  • Joined: 07 Nov 2013
  • Loc: Gulf Coast, Panhandle of Florida

Posted 30 December 2018 - 06:56 AM

I would use caution concerning annealing. If you mess up ANY part of the annealing procress...well...you have unannealed glass...which is useless for telescope making....



#25 totvos

totvos

    Viking 1

  • *****
  • Posts: 617
  • Joined: 09 Sep 2015
  • Loc: Mississauga, ON, Canada

Posted 30 December 2018 - 09:56 AM

I would use caution concerning annealing. If you mess up ANY part of the annealing procress...well...you have unannealed glass...which is useless for telescope making....

 

At the risk of being contrary, I am not sure it is as dire as all that. Yes, the glass needs to be annealed, but if you are going through this effort, you have likely already researched appropriate heating schedules and will have factored annealing time and temperatures into it. The “ANY” is simply time and temperature, and when it comes out of the kiln you simply do a strain test using polarized light to check your work. If for some reason you are not happy with the results, figure out what you did wrong and slump again.

 

I do not believe that “annealed” is a binary state. You are removing residual strain during annealing, and while you can expend a huge amount of time doing that (weeks for mega-$$$ telescope projects), practically speaking that is overkill for ATM.

 

I have found this process very forgiving.


  • PrestonE, brave_ulysses and Earthbound1 like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics